Stereoselective synthesis of C1–C12 fragment of amphotericin B

An efficient synthesis of C1–C12 fragment of amphotericin B is described. The synthesis is based on asymmetric dihydroxylation and cross-metathesis reactions.     

Synthetic studies on antascomicin A: construction of the C18-C34 fragment

Stereoselective synthesis of the C18-C34 fragment of antascomicin A is described. Construction of the C27-C34 carbocycle moiety was achieved via catalytic Ferrier carbocylization and Johnson-Claisen rearrangement, which was converted to iodide 2 by use of asymmetric alkylation and Sharpless epoxidation as key transformations. Coupling of iodide 2 and sulfone 3 furnished the C18-C34 fragment.     

Stereoselective synthesis of the C1-C20 segment of the microsclerodermins A and B

An enantioselective route for the synthesis of key fragment C1-C20 resident in microsclerodermins A and B is described. The route features deoxygenative rearrangement of an hydroxy-alkynoate and a highly enantio- and diastereo-controled iterative dihydroxylation as key reactions, starting from S-(−)-citronellol.     

A highly enantioselective synthesis of (−)- and (+)-juglomycin A through Dötz annulation and asymmetric dihydroxylation

A highly enantioselective synthesis of (−)- and (+)-juglomycin A, a quinone antibiotic is described. The synthesis is completed in eight steps, and 19% overall yield and in a high enantioselectivity of 99.5% [for (−)-juglomycin A] and 98.5% [for (+)-juglomycin A]. The synthetic strategy features an efficient combination of the Dötz annulation reaction and asymmetric dihydroxylation as the keys steps.     

3-[N-(4-甲基苯基)氨基羰基]-5-[4-(4-甲酸基苯甲氧基)苯亚甲基]-2,4-噻唑烷二酮的合成

以对甲苯胺和对甲基苯甲酸甲酯为起始原料,经NBS溴化、亲核取代、酸水解和Knoevenagel缩合等6步反应合成了抗细菌生物膜化合物—3-[N-(4-甲基苯基)氨基羰基]-5-[4-(4-甲酸基苯甲氧基)苯亚甲基]-2,4-噻唑烷二酮,总收率57.3％,其结构经1H NMR,ESI-MS和元素分析确证.     

A Facile Synthesis of the C-11 isomer of 5-epi-Kudtriol

Eudesmane derivatives contain a number of naturally occurring compounds. Amongthem many compounds possess intriguing biological properties"'.Kudtriol 1 and 5-epi-kudtriol 2 was first isolated from the aerial parts of Jasaniaglatinosa by Tereasa et al ', and their structures were determined as (-)-eudesm-4(14)-ensa,l 1,12-triol and ( )-eudesm-4(14)-en-50,l l,12-triol respectively by spectroscopicmethods.Although previous paper reported the synthesis of 2 from Q-santonin 4 in elevensteps#, an e…     

Synthetic studies on neomarinone: practical and efficient stereoselective synthesis of the side chain

A practical and efficient stereoselective synthesis of the side chain of neomarinone is reported. The synthesis was achieved in six steps (41% overall yield) from 2-methyl-2-cyclohexenone. The key step is a novel stereoselective 1,4-conjugate addition/enolate alkylation by an epoxide-opening reaction.     

Synthetic studies on borrelidin: enantioselective synthesis of the C1-C12 fragment

[structure: see text] An efficient, enantioselective synthesis of the C1-C12 fragment 2 of borrelidin is presented. Construction of the "skipped" polymethylene chain of 2 was accomplished by iteration of Myers' alkylation, while formation of the C3 stereocenter was achieved by Roush's asymmetric allylboration methodology.     

Total synthesis of topsentolide B2

A stereoselective total synthesis of topsentolide B₂, a selective cytotoxic oxylipin against SK-OV-3 and SK-MEL-2 cancer cell lines has been achieved based on asymmetric dihydroxylation, Roush allylation, and ring closing metathesis (RCM) reactions. The synthesis is completed in 11 steps and 2.1% overall yield.     

Synthetic studies on thiostrepton family of peptide antibiotics: synthesis of the dihydroquinoline portion of thiostrepton, the siomycins, and the thiopeptins

Synthesis of the dihydroquinoline portion of thiostrepton, the siomycins, and the thiopeptins, members of the thiostrepton family of peptide antibiotics, has been achieved featuring the one-pot olefination via the Matsumura-Boekelheide rearrangement “using trifluoromethanesulfonic anhydride and triethylamine” and the stereoselective addition reaction controlled by the stereocenter of the peri-position.     

Synthetic studies on pseudolaric acid B:Enantioselective synthesis of C4,C10-di-epi-trans-fused[5-7]-bicyclic skeleton

Studies on the synthesis of antifungal and anticancer natural product,pseudolaric acid B,have led to the enantioselective synthesis of di-epi-trans-fused [5-7]-bicyclic co re skeleton.The synthesis was achieved in 10 linear steps,which features the Sharpless asymmetric epoxidation,cyanide-opening reaction of epoxide,and intramolecular [5+2] cycloaddition reaction as the key transformations.The stereochemistry was determined by the X-ray crystallographic analysis.     

Concise stereoselective synthesis of cis-3-alkoxy-2-carbomethoxy medium-ring oxacycles from (R)-3-(3-butenyl)-4-propynoyloxazolidin-2-one

A concise process for the stereoselective synthesis of chiral cis-3-alkoxy-2-carbomethoxy medium-ring oxacycles from (R)-3-(3-butenyl)-4-propynoyloxazolidin-2-one (1) was developed. The process includes five major steps: (i) hetero-Michael reaction between an alcohol and 1, (ii) stereoselective reduction of the resulting ketone, featuring stereochemical assistance of the neighboring oxazolidin-2-one group, (iii) esterification with an alkoxy acetic acid, (iv) chirality-transferring Ireland-Claisen rearrangement of the resulting 3-alkoxyallyl glycolate ester to provide a syn-2,3-dialkoxy carboxylate ester, and (v) relay ring-closing olefin metathesis to form a medium-ring ether along with the simultaneous removal of the oxazolidin-2-one moiety.     

Green chemistry multicomponent protocol for formylation and Knoevenagel condensation for synthesis of (Z)-5-arylaminomethylene pyrimidine 2, 4, 6-trione derivatives in water

A green, efficient, and novel one-pot multicomponent protocol was developed to achieve stereoselective (Z)-5-(arylpropenylidine)-2,4,6-pyrimidinetrione derivatives using a three-component reaction involving appropriate aromatic amines, formic acid, and barbituric acid using water as green solvent by conventional thermal heating process. In this way, N-formylation of various amines takes place. The resulted different formamides undergo Knoevenagel condensation with active methylene group containing compound, that is, barbituric acid. The newly synthesized compounds were characterized by spectral analysis (Fourier Transform Infrared [FT-IR], 1H nuclear magnetic resonance [NMR], 13C NMR, Heteronuclear Multiple-Bond Correlation [HMBC], Mass, UV spectroscopy) and elemental analysis. The multicomponent reactions (MCRs) showed good stereoselectivity.     

The stereodivergent asymmetric synthesis of a range of 2-(1′-hydroxyalkyl)phenols

The use of the (S)-α-methylbenzyl group as a chiral auxiliary has allowed the diastereoselective ortho-deprotonation of a chromium tricarbonyl complexed phenoxy ring. When the resultant ortho-anion is treated with an aldehyde two diastereoisomeric complexes are formed, in relatively poor dr, which differ in the configuration of the newly formed benzylic stereogenic centre. However, both ortho-formylation followed by treatment with Grignard reagents and ortho-acylation followed by reduction with Super-Hydride^® were found to be completely diastereoselective, giving access to either epimer of the corresponding benzylic alcohol complexes in >99:1 dr. Subsequent oxidative removal of the chromium tricarbonyl unit, followed by cleavage of the O-α-methylbenzyl chiral auxiliary gives enantiopure 2-(1′-hydroxyalkyl)phenols. Following this stereodivergent procedure, either enantiomer of the product may be accessed from a single antipode of [(α-methylbenzyloxy)benzene]Cr(CO)₃.     

Synthetic studies on apoptolidin: synthesis of the C12-C28 fragment via a highly stereoselective aldol reaction

The stereoselective and convergent synthesis of the C12-C28 segment 2 of the apoptosis inducing macrolide antibiotic, apoptolidin (1), is described. The synthesis involves a highly stereoselective tin(II)-mediated aldol reaction between the C17-C22 ethyl ketone 3 and the C23-C28 aldehyde 4 as the key step.     

Synthetic studies on macrolactin A: construction of C4-C24 fragment

The preparation of the C4-C24 fragment of the macrolactin A is described. The adopted synthetic strategy involves two isomerizations to selectively construct the (8E,10Z) and (16E,18E) dienes, using a sequential Claisen rearrangement/allene isomerization and a Ph3P-catalyzed isomerization of an yne-one, respectively.     

Synthetic studies toward the total synthesis of tedanolide: assembly of the C1-C23 carbon backbone

A stereoselective assembly of the C1-C23 fragment representing the carbon backbone of tedanolide was accomplished utilizing a chiral boron reagent to effect the aldol coupling of the C1-C12 diketoester fragment with the C13-C23 aldehyde fragment.     

Stereoselective synthesis of the C9-C19 lactone-dipropionate fragment of calyculin C

A highly diastereoselective synthesis of the title fragment of calyculin C has been developed based on an internal asymmetric induction between a chiral aldehyde and Z-crotyl trifluorosilane.     

A concise and stereoselective synthesis of (+)- and (−)-deoxoprosophylline

An efficient synthesis of (+)- and (−)-deoxoprosophylline was accomplished from the readily available cis-2-butene-1,4-diol in which the Sharpless asymmetric dihydroxylation was used as the key step.     

Synthetic studies on the cornexistins: synthesis of (+/-)-5-epi-hydroxycornexistin

The synthesis of 5-epi-hydroxycornexistin (44), a diastereoisomer of the herbicidal natural product hydroxycornexistin (2) has been completed. Palladium mediated sp(2)-sp(3) coupling of the stannane 25 and the chloride 31 and ring-closing metathesis of the resulting diene 32 has been used to construct the tricyclic lactone 34a, which possesses the nine-membered carbocyclic core found in the natural product, in good yield. The synthesis of 5-epi-hydroxycornexistin (44) has established the feasibility of using a furan as precursor for the cyclic anhydride unit present in the natural product and has demonstrated the viability of other late-stage transformations that will be used to prepare hydroxycornexistin (2).